Germanwings flight 9525 was flying from Barcelona, Spain to Dusseldorf, Germany when the aircraft experienced a sudden loss of altitude.

All 150 passengers and crew on boards are believed to have perished. Reuters reported that there were three Americans on the flight.

While both "black boxes" have been found, it could be months or years before we know what caused the Airbus to go down.

"Everyone wants to come up with some sort of possible cause, and there's no way to do that. It could be one of a thousand things," airline pilot and author of the book "Cockpit Confidential" Patrick Smith told Business Insider.

Here's what we do know. The Airbus A320 is one of the most advanced, popular, and durable airliners in the world. With more than 11,500 sold and 6,200 planes in services, the A320 series is arguably Airbus' greatest success. With just 23 fatal incidents in a quarter century of flying, the 320 has an excellent service history.

This was Germanwings first fatal accident since the airline's founding in 1997. Parent company Lufthansa hasn't had a fatal crash in more than two decades.

"Lufthansa and Germanwings both have great safety records," aviation expert and founder of NYCAviation Phil Derner, Jr. said. "They've taken great steps to maintain a high level of safety."

Although the aircraft involved in the incident required maintenance twice in the two days prior to the crash, Lufthansa's CEO assured the public that the Airbus flew with a clean bill of health each time it took off.

REUTERS/ C.Chan
In fact, the European aviation system ranks as one of the most congested, and yet safest, in the world. With more than 30,000 flights per day covering 21 million nautical miles, accidents remain exceedingly rare.

None of this means that safety or a problem with the plane won't be identified as a factor in the crash. Authorities are perplexed, the New York Times reported, about the lack of communication between the plane's pilots and air traffic controllers during the relatively slow, 10-minute descent that preceded the A320's crash.

The plane's cockpit voice recorder was also damaged in the impact, potentially limiting investigators' ability to reconstruct the events of the accident.